Apparatus for producing molds



APPARATUS FOR PRODUCING MOLDS Filed Nov. 26, 1962 Fig. 4 Fig. 3

INVENTORS MICHAEL SCHAIBLE AND BY WAINWRIGHT TUTTLE,

WMIMKM ATTORNEYS.

United States Patent 3,216,071 APPARATUS FOR PRODUCING MOLDS Michael Schaible, Sudbury, Mass., and Wainwright Tuttle,

Cincinnati, Ohio, assignors, by mesne assignments, to

Altamil Corporation, Indianapolis, Ind., a corporation of Delaware Filed Nov. 26, 1962, Ser. No. 239,945 7 Claims. (Cl. 22-163) This invention relates to the formation of molds from sand or the like, and more particularly to the formation of a mold for casting an article having an undercut portion.

The formation of molds for casting is an old and well known art. The basic steps are the manufacture of a male pattern, and the formation of the mold from a suitable material around this pattern. It is conventional to form such molds as two mating elements. Similarly, the pattern is formed in two halves, each of which is usually secured to a perfectly flat pattern mounting plate. The moldable material is held in place around the pattern by a mold box and hardened in any well known manner. When the pattern and mounting plate are removed, the resulting mold half will usually have a perfectly flat surface with a cavity conforming to the pattern half. It will now be obvious that the pattern half (and hence the object being cast) must be so designed that it can be removed after the mold has been formed around it without destroying the mold.

In a companion case, Serial No. 331,558 we have taught a new method for forming cores and hollow castings which involves what we shall call hereinafter vertical parting of the mold. Vertical parting is simply a shorthand description of our novel method of orientation of the pattern with respect to the parting plane of the mold. That is, at least the longer axis of the pattern is perpendicular to the mold parting plane. This may be compared with a horizontal parting or conventional mold in which all the longer axes of the pattern are parallel to the parting plane of the mold.

As set forth in greater detail in that application, both horizontal and vertical parting offer certain advantages. But in the casting of many pieces, such as for example a bath drain T having enlarged threaded portions at each of its three openings, it has heretofore been necessary to utilize horizontal parting to prevent an undercut or lock, which would in turn prevent withdrawal of the pattern after formation of the mold.

It is therefore a primary object of our invention to provide a method by means of which a mold for an article having a lock or undercut may be formed, so as to make it possible to cast undercut articles with vertical parting of the mold.

A further object of our invention is the provision of an apparatus in the form of a novel construction for a pattern around which a mold for an article having an undercut may be formed.

A more specific object of our invention is to provide .an expandable pattern which may be expanded to predetermined dimensions during the molding operation (either before or after the moldable material has been placed around the pattern), and which may be returned to its original configuration for removal from the mold.

These various objects, along with others which will become apparent to a skilled worker in the art as this specification proceeds, are best accomplished by the method explained hereinafter, and by the apparatus illustrated in an exemplary embodiment in the accompanying drawings, in which:

FIGURE 1 is a vertical cross-sectional view through a pattern embodying our invention;

3 ,2 16,371 Patented Nov. 9, 1965 FIGURE 2 is a vertical cross-sectional view of a portion of the device illustrated in FIGURE 1 but showing the parts in a secondary position;

FIGURE 3 is a perspective view of a very important element of our invention; and

FIGURE 4 is a perspective view of a modification of the element shown in FIGURE 3.

These drawings illustrate the invention as applied to a bath drain T or valve body. Referring to FIG. 1, the half pattern may be described as a male element having a body portion 1 which will form one-half of the crosspiece of the T, and a body portion 2 which will form onehalf of the leg of the T. It will be understood that in this case, where the article being cast, is symmetrical, the two mold halves may be made from the same half pattern, while for other alticles, mating pattern halves are required. At any rate, two mold halves will be formed which when placed in the proper relationship, will form the cavity for the desired casting. It will be noted that the end of the body portion 2 is enlarged as shown at 3; this portion of the finished casting will be threaded in the final machining operation as is well known in the art.

Basically, it is this threaded or enlarged portion 3 which necessitated the development of the instant invention. In other words, when a T shape as the one illustrated is cast lying on its side in a horizontal parting mold (both the axis of the cross-piece and the axis of the leg being parallel to the parting plane of the mold), these enlarged portions may be formed in the mold without an undercut. However, it will be apparent from examining FIG. 2, that when one of these axes is perpendicular to the parting plane of the mold, such an enlarged portion (indicated generally at 4), will create an undercut or lock, which, after the sand has been hardened around the pattern, would prevent removal of the pattern.

To permit molding of undercuts, we provide the body portion 1 of the pattern with a passage in which is located a tube 5. The lower end of the tube 5 is threaded as at 6, so that it may be secured to the pattern mounting plate 7. Secured to the upper end of the tube 5 in any suitable manner is a cap 8. In the drawings, we have shown the cap as secured in place by means of the screw 9, but this is simply a matter of design.

The cap 8 is so designed as to perform a dual function. In the first place, its outside configuration will be substantially the same as the core print portion 10 of the pattern which is seen just to the right of the enlarged portion 3 of the pattern. As one well versed in the art of casting will of course understand, the formation of a hollow or cored casting requires the use of a separate core, which must be supported in the proper relationship with respect to the mold pattern. Therefore, the outside diameter of the cap 8 and of the core print portion 10 will be substantially equal to the desired inside diameter of the finished casting. The core which of course will be in the shape of a half T, will be made longer than necessary, and the elongated ends will be supported by the core print portions in the mold. The cap also serves to limit the size of the expandable member as will be explained hereinafter.

Returning now to the construction of the Cap 8 it will be seen that its inner surface is hollowed out to form an annular wall 11. Similarly, the end of the body portion 1 adjacent the cap 8 is also hollowed out to form an annular shoulder 12.

Mounted between the body portion 1 and the cap 8, and engaged by the wall 11, and the shoulder 12 respectively, is the expandable member 13. As seen in FIG. 1 (see also FIG. 3), this expandable member comprises a cylindrical portion 14, and an annular flange 15, located substantially centrally with respect to the portion 14, both of which are preferably formed from a suitable elastic material.

In its initial position, the cylindrical portion 14 will closely surround the tube 5 and the outside diameter of the flange 15 will be somewhat less than the diameter of the body portion 1.

To form a mold for an article having an under-cut or lock, fluid under pressure may be introduced into the tube 5. Fluid may be supplied to this tube in any conventional manner, but for the sake of showing a complete embodiment, there is shown in FIGURE 1 a slot 16 milled in the pattern supporting table 17, which it will be understood communicates with a suitable source of supply. I have found that this particular construction is preferable in the case where a number of patterns are to be used in a single mold box. In this manner, a single slot 16, and a single supply of fluid under pressure may communicate with a plurality of such patterns. The fluid may then travel upwardly through the tube 5, and out through the ports 18. The fluid emerging from the ports 18 will bear against the expandable member, forcing it outwardly to the position shown in FIG. 2, in which the cylindrical portion 14 will bear against the wall 11 and the shoulder 12 described above. In other Words, by careful selection of the size and position of the wall 11 and the shoulder 12 and the thickness of the cylindrical portion 14, the outer limits to which the expandable member will move may be determined with a high degree of accuracy.

It is well known that when an elastic member is expanded, it tends to get thinner; and in the case of a pattern such as contemplated in this application, this tend ency could produce undesirable result-s in that the moldable material could enter the space between the flange 15 or the body portion 1 and the cap 8. To counteract this tendency, I provide a central annular perforation 19 in the cylindrical member 14, and a hollowed out portion 20 in the annular flange 15. By this expedient the fluid under pressure emerging from the ports 18 may flow into the hollowed out portion 20 through the perforation 19, expanding the annular flange 15 against the top surface of the body portion 1 and the bottom portion of the cap 8.

After the moldable material has been formed around the pattern, the fluid pressure is exhausted. This may be accomplished by an exhaust valve connected to the slot 16. This will permit the elasticity of the member 13 to return it to its original configuration shown in FIG. 1, thereby leaving a cavity in the mold. It will now be apparent that the pattern can be Withdrawn without damage to the finished mold.

We have found that there are several satisfactory methods for utilizing the apparatus of our invention in the formation of molds of the character described. For example, the expandable member 13 may be expanded either before or after surrounding the pattern with the moldable material. Similarly, the member 13 may be maintained in its expanded condition until after the moldable material has been hardened or it may be returned to its original configuration after', filling the mold box with sand but before hardening. Specifically, expanding the member 13 after the moldable material has been placed loosely around the pattern, has the singular advantage of avoiding a recess under the expanded ring which would be hard to fill with molding material.

It will by now be apparent that numerous modifications may be made in our invention without departing from its scope or spirit. For example, in FIG. 4 we have indicated one common modification of the expandable member 13. In this modification, the portion 14a is cylindrical and very similar to the portion 14 heretofore described. However, it can easily be seen that the annular flange 15a is hexagonal. In other words, this apparatus can be effectively adapted to the casting of an enlarged hexhead.

Accordingly, we intend no limitation on this invention except insofar as set forth in the following claims.

What we claim as new and desire to secure by Letters Patent is:

1. A pattern for forming molds comprising a body portion, a cap secured to said body portion in spaced apart fixed relation, an expandable member secured between said body portion and said cap, means for expanding said member to a predetermined size, and means for returning said member to its original configuration while maintaining said spaced apart fixed relation of said cap and body portion.

2. The pattern claimed in claim 1 wherein said body portion of said pattern is provided with a passage, said passage communicating at one end with said expandable member and at the other end with a supply of fluid under pressure, whereby when fluid under pressure is applied to said passage said member is expanded and when said passage is opened to the atmosphere the fluid under pressure is exhausted thereby returning said member to its original configuration.

3. The pattern claimed in claim 2 wherein said expandable member comprises an elastic cylindrical element having a central perforation, and an elastic annular flange surrounding said element centrally thereof.

4. The pattern claimed in claim 3 wherein said annular flange has a hollowed out portion communicating with said perforation.

5. A pattern for forming molds comprising a body portion with an annular shoulder at one end, a cap secured to said body portion adjacent said shoulder and spaced apart therefrom, said cap having an annular wall depending therefrom and facing said shoulder, a resilient cylindrical element having a central perforation mounted between said body portion and said cap, one end of said element being engageable by said shoulder and the other end of said element being engageable by said wall, an annular flange surrounding said element centrally thereof, said flange having a hollowed out portion communicating with said perforation, means for expanding said cylindrical element and said flange to a predetermined size, and means for returning said cylindrical element and said flange to their original configuration.

6. The pattern claimed in claim 5 wherein said body portion of said pattern is provided with a passage, said passage communicating at one end with said central perforation of said cylindrical element and at the other end with a supply of fluid under pressure, whereby when fluid under pressure is applied to said passage said cylindrical element is expanded against said shoulder and said annular Wall and when said passage is opened to the atmosphere the fluid under pressure is exhausted thereby returning said cylindrical element to its original configuration.

7. The pattern claimed in claim 6 wherein said annular flange has a hollowed out portion communicating with said perforation, whereby when fluid under pressure is applied to said passage said cylindrical element is expanded against said shoulder and said Wall, and said flange is expanded to fill the annular space between said body portion and said cap.

References Cited by the Examiner UNITED STATES PATENTS 554,380 2/96 Smethers 22-163 720,718 2/03 Maddock et al. 22165 X 800,213 9/05 Jacobs 22-163 2,491,146 12/49 Zahn 22l63 2,582,922 1/52 Crowley et al 22163 2,903,762 9/59 Caudron 22-173 3,028,630 4/62 Walker 22165 J. SPENCER OVERHOLSER, Primary Examiner.

MARCUS U. LYONS, Examiner. 

1. A PATTERN FOR FORMING MOLDS COMPRISING A BODY PORTION, A CAP SECURED TO SAID BODY PORTION IN SPACED APART FIXED RELATION, AN EXPANDABLE MEMBER SECURED BETWEEN SAID BODY PORTION AND SAID CAP, MEANS FOR EXPANDING SAID MEMBER TO A PREDETERMINED SIZE, AND MEANS FOR RETURNING SAID MEMBER TO ITS ORIGINAL CONFIGURATION WHILE MAINTAINING SAID SPACED APART FIXED RELATION OF SAID CAP AND BODY PORTION. 